The present invention relates to a compressed air system for supplying a turbo-charged internal combustion engine. A compressor is connected to a reservoir vessel for supplying a compressed air blowing-in module, and a compressed air-conditioning device with an air dryer and a pressure regulator is provided for supplying pressure vessels for compressed-air-activated consumers.
German patent document no. DE 10 2006 008 783 discloses a fresh gas supply device for a turbo-charged turbo internal combustion engine. In said engine, a compressor is operated which has an air dryer arranged downstream of it in order to feed the dried air to a pressure chamber. The air dryer is continuously in operation when the compressor is operating, which entails comparatively high expenditure, in particular because the air to be dried consumes, in turn, approximately 10% of the quantity of air on regenerating the desiccant. Such a compressed air system can therefore be optimized in terms of installation space, weight and consumption.
Although an air dryer is necessary only to a limited degree for a compressed air blowing-in module for a turbo-charged internal combustion engine, if the compressed air is also to be used to operate other compressed air consumers such as a brake system, air suspension system and secondary consumers, an air dryer is important in order to avoid the pressure vessels and lines being filled with water, in particular because this can result in problems due to the formation of ice and corrosion.
An object of the present invention is therefore to provide a compressed air system for supplying a turbo-charged piston internal combustion engine whose operation is configured in an optimized and flexible way.
According to the invention, in the compressed air system the line for filling the reservoir vessel for supplying a compressed air blowing-in module is branched off upstream of the compressed air-conditioning device in the direction of flow of the air. As a result, although the compressor supplies both the reservoir vessel for supplying a compressed air blowing-in module and the compressed air-conditioning device, the supply is however via separate lines so that variable operation of the compressed air system is made possible. In particular, the entire quantity of air is no longer fed to the compressed air-conditioning device.
The compressor is connected via a first line to the pressure vessel for supplying a compressed air blowing-in module, and via a second line to the pressure vessels for compressed-air-activated consumers. By dividing the compressed air from the compressor into two lines it is possible optionally to make available a supply with compressed air to the compressed air blowing-in module and/or the pressure vessels for compressed-air-activated consumers. However, the duration of the compressed air supply can be adjusted individually.
According to one preferred embodiment of the invention, at least one switchable valve is provided in a line between the compressor and the compressed air-conditioning device in order to switch off the compressed air supply when the pressure vessels for compressed-air-activated consumers are sufficiently filled. As a result, the conditioning of the compressed air can be carried out whenever the corresponding pressure vessels are to be filled. If the pressure vessels are filled, the compressed air-conditioning device with the air dryer can be switched off, with the result that the air dryer can run through a regeneration phase. This procedure is particularly efficient because the high degree of consumption of energy for drying the air has to take place only in certain phases of the operation of the compressed air system and regeneration of an air dryer cartridge is made possible.
In order to avoid a backflow in the line to the compressed air blowing-in module, a non-return valve can be arranged upstream of the pressure-limiting valve. A backflow is avoided in particular when the venting valve is switched.
A first control signal is preferably generated by corresponding pressure sensors if a maximum pressure is reached downstream of the non-return valve, and a second control signal is generated if a predetermined maximum pressure is reached in the line for supplying the compressed air-conditioning device. In addition, a logic switching device can be provided which generates a third control signal if the first and second control signals are present. This makes it possible to actuate, preferably by the third control signal, a venting valve which is arranged in a feed line of the compressor, in particular upstream of the branching of the lines. Alternatively it is possible to use the third control signal to actuate a valve of an energy-saving system by which the compressor can be switched off.
A pressure-limiting valve is preferably arranged in the line between the compressor and the pressure vessel for supplying a compressed air blowing-in module. This ensures that when a predetermined pressure is exceeded, the compressor and/or a venting valve can be switched off, in particular if the compressed air blowing-in module no longer requires any compressed air.
According to a further embodiment of the invention, the venting valve is arranged in a feed line of the compressor upstream of a branching of the lines to the compressed air blowing-in module and the pressure vessels for compressed-air-activated consumers and is of switchable design. The switching is preferably carried out using control signals which are generated by the pressure-limiting valve and the switchable valve upstream of the compressed air-conditioning device. In particular, the venting valve can be switched off automatically if the overpressure valve closes and the compressed air-conditioning device no longer requires any compressed air. It is possible for this, for example, to provide a logic valve for switching the venting valve.
An overflow valve which has a higher opening pressure than at least one pressure vessel for compressed-air-activated consumers is preferably provided in the line to the compressed air blowing-in module downstream of the pressure-limiting valve. As a result, the filling sequence of the pressure vessels can be predefined.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.